Work on the purification of the neurosecretory hormone that regulates egg development in mosquitoes (Egg Development Neurosecretory Hormone, EDNH) has progressed. High pressure liquid chromatography techniques are being used. EDNH has the same effects in vitro and in vivo, but females will not respond until 2 hours after a blood meal. Juvenile hormone controls the competence of the ovary to respond to EDNH. Work on the purification of EDNH will continue. We plan to further characterize the response of mosquito cell lines to EDNH. The response of the whole animal to EDNH will be investigated further; in particular, we want to ask why a blood meal is required before the female can respond.